The inability to unmount a file system or device typically indicates active processes or open files are still utilizing it. For example, a user might have a terminal open in a directory within the targeted file system, or a program could be actively reading or writing data to it. Even something seemingly minor, like a file manager displaying the contents of the target, can prevent unmounting.
Preventing accidental data corruption or system instability is a primary reason why this safety mechanism exists. Forcefully unmounting a busy file system can lead to incomplete write operations, corrupted files, and potentially even system crashes. Historically, the concept stems from the physical act of dismounting storage media like tapes or disk packs. Just as one wouldn’t physically remove a tape while it’s being read or written to, unmounting a busy file system introduces similar risks in a digital context. Ensuring clean unmounting contributes to data integrity and reliable system operation.
